r - 在 as.numeric() 中避免 NA

Question

如果我这样做，我会得到正确的结果:

a <- c("10","28","3")
which(as.numeric(a) == min(as.numeric(a)))
[1] 3

但是如果向量中有NA，那就有问题了

a <- c("10","28","3","NA")
which(as.numeric(a) == min(as.numeric(a)))
integer(0)
Warning messages:
1: In which(as.numeric(a) == min(as.numeric(a))) :
  NAs introduced by coercion
2: In which(as.numeric(a) == min(as.numeric(a))) :
  NAs introduced by coercion

Answer 1

两件事情。

首先，字符串"NA"之间有区别。和缺失值的 R 数据表示，NA .删除示例中 NA 周围的引号以查看:

a <- c("10","28","3",NA)

其次，当您使用 min 时带有实际缺失值(即不是字符串 "NA" )，您需要使用 na.rm = TRUE :

which(as.numeric(a) == min(as.numeric(a),na.rm = TRUE))